Recall that the potential danger associated with an electromagnetic wave…

The idea

This recall point links the electromagnetic spectrum to hazard. As frequency rises across the spectrum, from radio waves through microwaves, infrared, visible light, ultraviolet, X-rays to gamma rays, the energy carried by each photon increases, so the potential to damage living cells grows. Radio waves are low frequency and low hazard; gamma rays are high frequency and high hazard. The key relationship to remember is that potential danger increases with increasing frequency. Note that this is about potential danger per wave, not about the total energy delivered, which also depends on intensity and exposure time.

What earns the marks

• States that potential danger increases as frequency increases.
• Places higher-frequency waves such as gamma rays and X-rays as more hazardous than radio waves.
• Recognises that the relationship is about frequency, not wavelength or amplitude alone.
• Applies the trend correctly when comparing two named regions of the spectrum.

Common mistakes and how to put them right

• Claims danger increases with wavelength.

  Put it right by linking danger to increasing frequency.

• Treats all electromagnetic waves as equally dangerous.

  Put it right: Recognise the frequency-dependent trend.

• Confuses intensity or exposure time with frequency.

  Put it right: Keep the stated relationship about frequency.

Exam tips

• Read the question to see whether it asks about frequency or wavelength before answering.
• Recall the order of the spectrum so you can rank two named waves quickly.
• Choose the option that states danger increases with frequency, not the reverse.